1. Field of the Invention
This invention relates in general to degasification devices and to a new and useful method and apparatus for cooling and dedusting degasification gases which escape from coal degasification chambers.
2. Description of the Prior Art
It is well known and in many cases usual to bring the hot degasification gases in the bends into contact with circulated cooling and scavenging water having temperatures below 100.degree. C. In such a process, the gases, while becoming saturated with steam, are cooled down from about 800.degree. C. to about 80.degree.-85.degree. C. and crude tar and water are separated in the collecting main.
For this purpose, 3.5 to 7.0 m.sup.3 of water per metric ton of coal are charged into the oven chambers and are sprayed in bends or collecting mains. Among others, the quantity of spray water depends on how much water is needed for precipitating the coal dust, which is entrained into the bends particularly at the start of the carbonization and for preventing it from being carried by the gas stream into the gas treatment apparatus, and for preventing deposits in the bends and collecting mains. Water, however, as is well known, is a poor wetting agent for coal dust.
The consequence of such a cooling method is that a tar-water mixture with a high water content and tending to emulsification is obtained in the collecting mains and that both the tar and the water components are contaminated with coal dust, and large apparatus are necessary for separating the tar-water mixture and obtaining water of such purity that it can be recirculated to the collecting main without causing disturbances in operation. But the content of solid matter and water in the tar also must not exceed predetermined limits, since otherwise the tar cannot be treated and sold without problems.
It would facilitate the operation of a coking plant if the scavenging of the collecting main and cooling of gas could be effected in a manner such as not to obtain any tar-water mixture at all in the collecting main and to obtain substantially only crude tar in liquid phase.